A wide variety of heart valve prostheses have been developed to operate hemodynamically, in conjunction with the pumping action of the heart, to take the place of defective natural valves. These valves are designed to function with valve members both in the form of a single occluder and a pair of occluders or leaflets, which valve members pivot along an eccentric axis (or both pivot and translate) to open and close a central blood flow passageway through the valve body.
U.S. Pat. No. 4,272,854 (Jun. 16, 1981) shows an early version of a bi-leaflet heart valve having an ear extending from each lateral side of the leaflet which pivots in a recess, guided in part by a knob which travels in a longitudinal slot that is cut more deeply into the sidewall of the valve body.
U.S. Pat. No. 4,373,216 (Feb. 15, 1983) discloses both single occluder and bi-leaflet heart valves wherein protrusions, extending radially inward from the flat sidewall sections of the valve body, guide valve members which have slots in their lateral edges to receive such protrusions.
U.S. Pat. No. 4,308,624 (Jan. 5, 1982) discloses heart valves of the single occluder and bi-leaflet type which have curved valve members which both rotate and translate in moving between the open and closed positions. Although the leaflets are intended to be able to assume a parallel orientation in the open position, as shown in FIG. 3, study of the arrangement shows that, upon reversal of blood flow through the passageway, the leaflets could translate upstream without beginning to rotate toward the closed position. Although pivoting could occur in the intended manner, once the leaflets have moved upstream guided by the path the spherical ears trace in the slots 21, one or both of the leaflets might possibly counterrotate, depending upon the instantaneous attitude of blood flow, and thereby not close on that stroke. U.S. Pat. No. 4,443,894 (Apr. 24, 1984) discloses a later version of this general type valve and illustrates an embodiment wherein the leaflets in their open position are angled relative to the centerline plane (see Column 4, lines 39-43) so that, when flow reversal occurs (as depicted in FIG. 4), the alignment of angled surfaces 44 of the stops 41 and their placement is such that there can be no inward pivoting or counterrotation of the leaflets (see Column 5, lines 34-41).
U.S. Pat. No. 4,451,937 (Jun. 5, 1984) shows additional single occluder and bi-leaflet valves wherein valve members, arranged at an angle to the centerline plane in the open position, pivot and translate to a closed position guided, in part, by laterally extending ears 21 which move in generally arcuate slots or depressions 23.
U.S. Pat. No. 4,328,592 shows other alternative embodiments of heart valves of this general type including some which have elongated slots in the valve sidewall with grooves to permit controlled leakage.
U.S. Pat. No. 4,692,165 (Sep. 8, 1987) discloses single occluder and bi-leaflet valves wherein valve members are guided in pivotal and translational movement in part by notches in their lateral edges which receive arcuate posts protruding from flat sidewall sections of the valve body.
U.S. Pat. No. 4,863,458 (Sep. 5, 1989) discloses bi-leaflet heart valves having leaflets of varying thickness which are guided in translational and pivotal movement by laterally extending ears that are received in recesses formed in the flat sidewall sections of the valve bodies.
Commercially developed heart valves using valve members of this type, as generally exemplified by the last 3 U.S. patents mentioned above, have employed valve members which are oriented at an angle to the centerline plane in the open position, so that the backflow of blood will preferentially impinge upon the outflow surfaces of each valve member and thus tend to initially impart a pivotal component to its movement toward closing. It is now felt to be particularly important that mechanical heart valve prostheses should provide passageways through which blood will flow freely with a minimum of drag in the open position and, to accomplish such end, that valve members should be able to assume an orientation which is parallel to the longitudinal axis of the passageway when the blood flow through the valve is at a high level; but, of course, these valves should also close quickly upon the occurrence of backflow to minimize regurgitation of blood. Improvements in construction to create mechanical valves having such characteristics have continued to be sought.